Washing machine

ABSTRACT

A power drive in a washing machine oscillates an agitator with a positive drive and spins a basket with a limited torque for gradual spin-up. The arrangement includes a transmission for selectively driving either the agitator or the basket as determined by the direction of rotational input. The drive to the transmission includes a one-way clutch adapted to positively drive the transmission in the agitation direction and a slip clutch to drive the basket with a predetermined torque in the opposite spin direction. A rotatable housing of the transmission forms both a sealed enclosure and a rigid structure in which a gear train is mounted. The housing has two mating sections in each of which are mounted spatially independent gear sets connected by a common pivotal link whereby critical gear center to center distances between housing sections are eliminated.

United States Patent 1 Archbold Jan. 8, 1974 4] WASHING MACHINE [75] Inventor: Ralph L. Archbold, Euclid, Ohio ABSTRACT 7 Assignee; Franklin M f t i Company, A power drive in a washing machine oscillates an agi- St. Cloud, Minn tator with a positive drive and spins a basket with a limited torque for gradual spin-up. The arrangement [22] Flled: 1972 includes a transmission for selectively driving either 21] App] 24 ,422 the agitator or the basket as determined by the direction of rotational input. The drive to the transmission includes a one-way clutch adapted to positively drive [52] US. Cl. 68/23.7 the transmission in the agitation direction and a i [5]] II!!- Cl. D06f 23/04 clutchgto drive the basket i a predetermined torque [58] Fleld of Search 68/23.7, 23.6 in the opposite Spin direction A rotatable housing of I the transmission forms both a sealed enclosure and a [56] References C'ted rigid structure in which a gear train is mounted. The

UNITED STATES PATENTS housing has two mating sections in each of which are 7 3,090,472 5/1963 Morrison 68/23.7 x mounted Spatially independent gear Sets connected y 2,75l,773 6/1956 Woodson 68/23.7 a common pivotal link whereby critical gear center to 2,976,746 3/1961 Flannery 68/23.7 X

center distances between housing sections are eliminated.

PMENTED 8 3,783 .652

SHEET 2 8F 2 WASHING MACHIN BACKGROUND OF THE INVENTION The invention relates to improvements in washing machines and more specifically to an improyed mechanical power drive system for selectively spinning and agitating appropriate machine members.

Machines of the type in which the present invention may be readily employed are generally embodied as automatic washing machines in which clothing or other fabric articles are immersed in water and washed under the influence of an oscillatory agitator. Subsequent to the washing operation, a perforate basket in which the articles are held is rotated at high speed to centrifugally extract rinse water from the articles and basket.

Normally in such a machine, a mechanical transmission is provided to reduce the speed of a drive motor and to convert its rotary motion into oscillatory motion for efficient operation of the agitator. Additionally, the transmission usually includes means to rotate the basket at a rate fast enough to cause the rinse water to be centrifugally drawn from the articles.

As a major component of a washing machine, the power transmission system generally accounts for a significant portion of overall machine manufacturing cost. A reduction in the number and manufacturing complexity of various subparts results in economic savings to a manufacturer particularly when such reductions are not reflected by a loss of function or reliability. Further, the transmission system may comprise a substantial portion of the weight of the machine and may thereby significantly affect shipping costs. Reductions in such shipping costs provide savings to the ultimate consumer and result in desirable competitive advantages for the manufacturer.

SUMMARY OF THE INVENTION According to the invention, a power drive system includes clutch means wherein delivered torque output during a basket spin mode is advantageously limited to a predetermined level while positive torque drive is available for an agitation or wash mode.

Preferably, the power transmission is of the type in which its operational mode, either agitation at reduced cyclic speed or spin at high speed, is determined by the direction of rotational input. When being driven in a direction corresponding to the spin mode, torque supplied by a driving motor is restricted by a slip clutch having a predetermined torque transmitting capacity. This restricted torque limits spin up acceleration of the basket to permit articles to uniformly distribute themselves in the basket to achieve a balanced condition for high speed spin.

The torque limiting clutch is not significantly affected by operating speed and therefore is capable of delivering maximum torque at both low and high speeds so that basket acceleration is uniform. The torque limiting feature of the slip clutch also affords motor overload protection in a spin cycle when a basket load is unbalanced. An uneven distribution of articles in the basket may cause excessive loading in the drive system and require substantially more power for driving the basket at full spin speed. Slippage provided by the clutch limits the loading or power draw on the motor to protect it from damage in such situations. in the preferred embodiment, the slip clutch is provided on a low speed shaft, separate from the motor, so that wear in the clutch is minimized.

In agitation, the transmission is driven in a rotational direction opposite to that of the spin mode. In this direction, the transmission is positively driven by a oneway clutch so that the torque available to drive the transmission is not limited by the previously mentioned slip clutch. In the agitation mode there is little chance of the motor being continuously overloaded, such as by an out of balance condition, so that torque limiting means is not necessary. In fact, it is desirable that the transmission be positively driven in agitation so that all slippage is prevented in order that the amplitude of oscillation of the agitator is maximized for greatest washing efficiency. Further, the absence of slippage in the agitation cycle minimizes clutch wear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a washing machine with an outer casing and certain other inner parts in cross section to reveal general details of a power transmission drive system.

FIG. 2 is an elevational cross sectional view of a transmission and other drive system components on an' enlarged scale from that illustrated in FIG. 1.

FIG. 3 is an exploded perspective view of the transmission with portions of its housing broken away to show various details therein.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, an automatic type washing machine for washing clothes and the like has been selected to embody the principles of the invention. An outer case or cabinet 12 forms the external dimensions of the machine 10 and provides the basic structure on which various other members and components are mounted. Clothes or other fabric articles are loaded into a circular perforated basket 13 through a hinged door (not shown) at the top, designated 14, of the housing 12. A suitable control system (not shown) is provided to initiate various conventional machine functions in a predetermined sequence. These functions chiefly comprise filling a tub 16 with wash water, causing an agitator 17 to be oscillated, draining the tub l6, filling the tub 16 one or more times with rinse water, and finally spinning the basket 13 to centrifugaily extract water from the articles therein.

. ket 13. The discussion following explains how these functions are derived through a power drive system 19 in the lower portion of the cabinet 12. The power drive system 19 includes a transmission 21 which has two aitemative modes of operation. In a first mode, the transmission 21 operates to oscillate the agitator l7 and in the second mode the transmission spins as a unit to rotate the basket 13.

The power drive system 19 also includes a reversible electric motor or other prime mover 22 with an output shaft 23 adapted to rotate about a vertical axis. A pump 24, driven by the output shaft 23, operates to discharge fluid from the tub 16 at a proper time in a sequence determined by the control system. The pump 24 is connected to the tub 16 by a suitable hose (not shown). Ideally, the motor 22 is adjustabiy fixed on a horizontally extending mounting plate 26 to permit a drive belt 27 to rotatably drive the transmission pulley 28 from the drive pulley 29 on the shaft 23.

Referring now more particularly to FIG. 2, for purposes of understanding the structure and operation of the transmission 21 it is helpful to realize that when the pulley 28 is driven in one direction by the motor 22, rotary motion of a transmission input shaft 31 on which the pulley is mounted is converted in the transmission to oscillatory motion in an output shaft 32 which is keyed or otherwise drivingly connected to the agitator 17. Alternatively, when the pulley 28 is driven in the opposite direction, rotation of the input shaft 31 causes rotation of the entire transmission 21 including an upper tube extension 33, keyed or otherwise drivingly connected to the basket 13.

Returning to a discussion of the structural details, as shown in FIG. 2, a lower bearing housing or block 36 having a square or similarly shaped exterior is received in a similarly shaped pocket or recess 37 stamped or otherwise formed in the horizontal mounting plate 26. A layer of elastomeric material 38 such as neoprene provides for resilient mounting of the lower bearing housing 36 in the mounting plate 26. Deformation of the elastomeric material 38 permits self-alignment of the lower bearing block 36 with respect to the various members mounted thereon. Additionally, the elastomeric material 38 absorbs or cushions vibrational forces developed in the lower bearing block 36 and reduces their effect on the remainder of the machine. The outer race of an anti-friction bearing 41 is pressed into a counterbore 42 in the lower bearing block 36. The bearing 41 is axially retained against a radial face 43 of the counterbore 42 by a circular snap ring 44.

The transmission 21 includes separable upper and lower housing sections 46 and 47, respectively, which may be machined from suitably formed metal castings. The lower housing 47 has at its lower end a hub or collar portion 48 which is vertically supported on the inner race of the bearing 41. A lower housing extension tube 51 is tightly received in a cylindrical bore 52 in the hub portion 48 and secured therein by a retaining pin 53 in a cross hole centered on a line tangential to the outer surface of the extension tube. The lower housing extension tube 51 extends downwardly through the inner race of bearing 41 with a slight interference fit so that the transmission 21 is thereby journaled in the bearing 41.

The lower bearing housing 36 and lower transmission housing section 47 include coaxial outer cylindrical surfaces 56 and 57 respectively on which an inner diameter of a helical spring 55 seats. The spring 55 operates as a brake in a well known manner by limiting rotation of the transmission housing sections 46 and 47 to one direction relative to the lower bearing housing 36. In the other direction the spring 55 locks the transmission to the non-rotating bearing housing 36. Desirably, the spring brake or clutch 55 is protectively covered by a boot 59 of rubber or the like and a wick 60 saturated with oil.

The upper transmission housing section 46 includes a cylindrical bore 66 in which is securely positioned the upper tube extension 33. Like the lower housing section 47 and extension 51, the extension tube 33 is retained in the cylindrical bore 66 by a cross pin 67. When the housing sections 46 and 47 are properly assembled the axes of their respective bores 66 and 52 are substantially coincident so that, as will be understood, the input shaft 31, the output shaft 32, and the transmission 21 are all capable of rotating about a common axis.

The upper tube extension 33 is journaled in a sleeve bearing 71. The sleeve bearing 71 is pressed into a bushing 72 which is molded in an upper bearing housing 73 formed of rubber or other elastomeric resilient material. The housing 73 is provided with a peripheral groove 74 which cooperates with an axially extending flange 75 forming an aperture in the tub 16 for mounting of the housing thereon. The resilience of the bearing housing 73 permits the bearing 71 to align itself with the extension 33 journaled therein and tends to absorb vibration in the extension. The housing groove 74 is dimensioned with respect to the flange 75 to form a water tight seal therewith so that water in the tub 16 may not leak past the housing. A dynamic seal, indicated generally at 77, is provided on the upper face of the housing 73 to seal against the outer surface of the extension tube 33 to similarly prevent water from escaping from the tub 16.

A plurality of angle straps or legs 81 (FIG. 1) rigidly fix the tub 16 relative to the horizontal mounting plate 26. Accordingly, the transmission 21 is rotatably suspended in the upper and lower bearing housings 73 and 36 along a generally vertical axis. A circular snap ring 78 disposed in a circumferential groove in the extension tube 33 limits upward axial movement of the transmission 21 by abutting a lower face of the sleeve bearing 71.

The upper tube extension 33 extends through a flange 83 which is centered in an aperture 84 in the basket 13 and is secured thereto by suitable fastners (not shown). The flange 83 is locked to the tube extension 33 by a suitable key 86 disposed in a flat 87 formed on the exterior of the tube extension. The basket 13 is thereby rigidly fixed on the extension 33 for rotation therewith.

Turning to a discussion of the structure for driving the transmission 21, the pulley or disc 28 includes a central axially extending hub 91 in which a radial sleeve bearing 92 is retained by a press fit. From the hub 91, a web 93 extends radially outward to form a circumferentially continuous radial friction face 94. A conical flange 96 joins the web 93 and a peripheral belt receiving groove 97. A short cylindrical collar 98 is fixed to the transmission input shaft 31 by a pin 99. An outer cylindrical surface 101 of the hub 91 has approximately the same diameter as that of the collar 98. A helically wound spring 102 having a slight interference fit with the cylindrical surface 101 and the collar 98 forms a one way clutch for transmitting torque between the pulley 28 and collar 98 in a conventional manner. The spring 102 is adapted to positively drive the shaft 31 when the pulley 28 is driven in a direction corresponding to an agitation mode of the transmission which direction is the same as that in which the spring clutch 55 brakes the transmission 21. The spring 102 is protected from contamination by a rubber boot 103 and oil saturated wick 104.

The pulley 28 is also adapted to drive the transmission input shaft 31 through a slip clutch arrangement 105 that comprises a washer-like pad of friction material 106 suitably secured to an apertured disc or plate 107. The plate 107 is biased towards the pulley 28 by a spider type resilient spring 108. The spring 108 is locked to a collar 109 which, inturn, is keyed against relative rotation on the shaft 31 by means of a flat 111 formed on the exterior of the shaft 31. Angularly spaced fingers or legs of the spider spring 108 mesh with corresponding slots 112 in an axially extending flange 113 of the plate 107. A nut 114 is threaded onto the end of the shaft 31 to axially retain the collar 109 thereon. The nut 114 may be adjusted axially'to vary the friction force between the pulley face 94 and friction material 106 to determine a predetermined slip torque.

The transmission input shaft 31 is joumaled in a pair of sleeve bearings 116 and 117 retained in upper and lower ends of the lower housing extension tube 51. A pinion gear 121 is fixed to the upper end of the input shaft 31 by a cross pin 122. A helical spring 123 is positioned on the exterior of an upper portion of the extension tube 51 and a cylindrical hub portion 124 of the pinion 121 having substantially the same diameter as the extension tube. The spring 123 is dimensioned to provide an interference fit between these members 51 and 1531 so that the spring forms a one way clutch for transmitting torque between the input shaft 31 and the lower transmission housing 47 only when the input shaft is driven in a direction corresponding to a basket spin mode.

A first stage in reduction of input shaft speed is provided by a gear 126 meshing with the pinion gear 121. A second stage of speed reduction is provided by a second pinion gear 127, integral with the gear 126, and a meshing gear 128. The integral gears 127 and 126 are rotatably mounted on a stub shaft 129 pressed into a vertical bore 130 in the lower transmission housing 47. Similarly, the gear 128 is rotatably mounted on a stub shaft 131, as illustrated in FIG. 3, which is suitably pressed into a vertical bore (not shown) provided in a boss 132 on the underside of the lower housing section 47.

A sector gear 136 is pivotally mounted on a stub shaft 137 pressed into a vertical bore 138 in the upper trans mission housing 46. The sector gear 136 is retained on the shaft 137 ,by a C washer 139. A pinion gear 141, fixed to the output shaft 32 by a cross pin 142, meshes with the sector gear 136. A driving connection between the gear 128 and sector gear 136 is provided by a rigid link or connecting rod 146 which transmits forces between these members along a plane perpendicular to the input and output shafts 31 and 32. The link 146 ineludes integral oppositely extending cylindrical projections 147 and 148 which provide means for connecting the link to the gear members 128 and 136. The projection 147 is pivotally received in a close fitting hole 151 in the output gear 128 in the lower housing 47 while, similarly, the other projection 148 is pivotally received in a close fitting hole (not shown) in the sector gear 136 in the upper housing 46.

The output shaft 32 is joumaled in a pair of sleeve bearings 156 and 157 pressed into the upper and lower ends of the upper tube extension 33. At an upper end 158 of the output shaft 32 a nut or other device (not shown) is provided to lock the agitator 17 onto the shaft 32.

As most clearly illustrated in FIG. 3, the housing sections 46 and 47 are separable at a plane perpendicular to the transmission shafts 31 and 32 and along the connecting rod 146 so that the plane of separation extends through the lower cylindrical projection 147. Desir- 6 ably, the stub shafts 129 and 131 terminate approximately at the plane of separation while the stub shaft 137 terminates adjacent this separation plane.

Bolts (not shown) extend throughaligned holes 161 and 162 in the upper and lower housings 46 and 47 to secure these sections together. One or more dowel pins 163 may be pressed into suitable holes in one housing section 47 while cooperating holes are formed in the opposite section 46 to permit the housing sections to be indexed to one another on the plane of separation. A gasket 164 is positioned between the housing sections 46 and 47 to eliminate leakage along the plane of separation. A threaded port 165, partially shown in FIG. 3, on the upper housing 46 permits the housing to be filled or emptied of lubricant after a threaded plug (not shown) is removed therefrom.

A principal feature of the transmission 21 is that the gears of each meshing set are mounted on the same transmission housing section. In the lower section 47, the gear 126 meshing with the input pinion gear 121 is mounted on the lower section. Similarly, the pinion 127 and meshing gear 128 are mounted in the same housing section 47. In the other housing 46, the meshing gear sector 136 and output pinion 141 are similarly mounted in the same integral structure. This arrangement makes it relatively easy to accurately hold all critical center to center distances when machining the respective housing sections for mounting of meshing gears. Connecting the driving elements or gears of the separate transmission sections with the connecting rod 146 eliminates any need for holding mutual gear center to center distances between the housing sections 46 and 47. This elimination of dimensional tolerances of the placement of gears in one section relative to the gears in the other section greatly simplifies machining procedures and thereby results in a transmission 21 relatively economical to produce. Similarly, assembly of the housing sections 46 and 47 relative to one another is not critical so that assembly costs and errors are reduced.

The entire tub assembly, transmission and drive motor are mounted for movement in the case or cabinet 12 by a suspension system which may by way of ,reference be constructed in a manner similar to that disclosed in US. Pat. No. 3,493,1 l8 granted Feb. 3, i970, to B. L. Brucken.

The support legs 81 are welded or otherwise secured to an inverted domed plate having a generally spherical surface 171. Facing this spherical surface 171 is a similarly shaped surface 172 provided by a lower panel 173 of the cabinet 12. The basket 13 and tub 16 and their contents, the agitator l7, transmission 21 and motor 22 along with various other associated parts are vertically supported by an annular shuttle ring 176 disposed between the domed surfaces 171 and 172. The tub 16 is horizontally centered or biased to the position illustrated in the Figures by suitably positioned springs 174 (one is shown) attached to the domed plate 170 and anchored in the cabinet 12. Similarly, the tub 16 is vertically biased by hold down springs 175. As disclosed in US. Pat. No. 3,493.1 18, the shuttle 176 minimizes transmission of lateral disturbing forces to the cabinet 12 such as produced by a spinning unbalanced load in the basket 13. t

From the foregoing structural description, operation of the power drive system, for the most part, is self explanatory. Under the control of an electric control timer and associated switching circuits, for example, the motor 22 is driven in a first or agitating direction. In this first direction, the spring clutch 102 positively drives the input shaft 31 through the collar 98 thereby causing the gears 121, 126, 127 and 128 to rotate. The rotational speed of the final gear 128 is substantially less than the speed at which the input shaft 31 is rotated. In the manner of a crank, rotational movement of the gear 128 is converted to oscillatory motion of the sector gear 136, forces developed in the gear 128 being transmitted by the connecting rod 146 to the sector gear 136.

Oscillation or rocking of the sector gear 136 causes a corresponding oscillation of the output pinion 141 and output shaft 32. The sector gear 136 and output pinion 141 are proportioned to yield an angular oscillation in the output shaft 32 and, ultimately, the agitator 17 of approximately 180 or more. As stated before, the spring clutch 55 operates to brake or prevent rotation of the transmission 21 in the direction that the input shaft 31 rotates to oscillate the agitator 17. Reaction forces set up by the agitator 17 or the gear train of the transmission may cause the basket 13 and transmission 21 to rotate a negligible distance each time the agitator 17 changes direction but such slight movement has an insignificant effect on the performance of the machine 10.

At a proper time in the operation of the machine, the timer control will cause the motor 22 to reverse its direction from that used in the agitation mode and thereby cause the basket 13 to spin. in this case, the spring clutch 102 is incapable of driving the input shaft 31 and torque is transmitted to this shaft through the slip clutch 105. Limitation of the torque applied to the input shaft 31 during start-up in the spin cycle is highly advantageous since limited angular acceleration of the basket 13, initially, permits articles therein to arrange themselves evenly about the circumference of the basket. Further, an unbalanced load developed by poor distribution of the articles in the basket may, without the limited loading of the motor provided by the slip clutch, cause the motor to be overheated. On the other hand, during agitation it is desirable that the agitator be positively driven to eliminate unnecessary wear otherwise caused by intermittent clutch slippage.

When being driven in the spin direction, the input shaft 31 drives the transmission 21 in unison through the spring clutch 123. The spring clutch 55, as mentioned, will permit the transmission 21 to rotate in such direction. Since the whole transmission 21 including the gear 126 rotates with the input shaft and, in particular, with the input pinion 121 there is no oscillatory output from the transmission to the output shaft 32 and hence the agitator l7 merely spins with basket 13 without agitation. From the foregoing description it may be appreciated that the power drive system 19 is relatively simple in construction and operation and results in substantial savings in overall manufacturing costs, bulk and weight while favorably improving machine reliability.

Although a preferred embodiment of this invention is illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed and claimed herein.

I claim:

1. In combination in a washing machine a drive pulley comprising a disc having a generally radial web extending outwardly towards a circular periphery, a belt receiving groove on said periphery, a central portion of said disc defining an axially extending-hub, radial bearing means in said hub adapted to permit rotation of said pulley on a shaft extending therethrough, a second disc carrying a generally radial friction face parallel to said radial web, means for locking said second disc onto said shaft, a resilient element biasing said friction face into constant engagement with said radial web with a predetermined force, and one way clutch means for transmitting torque between said shaft and said pulley.

2. The combination as set forth in claim 1 including a motor and a transmission for reducing the speed of said motor, said shaft being mounted on and providing a torque input to said transmission.

3. A power drive system for a washing machine comprising a reversible rotary motor, an article receiving basket, an article agitator in the basket, a transmission including a rotatably mounted housing, an input shaft rotatably mounted in the housing, the transmission having within its housing means to reduce the speed and convert rotary motion of the motor to oscillating movement in the agitator when said input shaft is driven in one rotary direction and one-way clutch means coaxial with said input shaft to spin said housing and said basket when said input shaft is driven in the opposite direction, one-way brake means coaxial with said input shaft preventing rotation of said housing in said one direction, a drive pulley rotatably mounted on said shaft and driven by said motor through a drive belt, said drive pulley including a disc having a generally radial web extending outwardly towards a circular periphery, a belt receiving groove on said periphery, a central portion of said disc defining an axially extending hub, radial bearing means in said hub adapted to permit rotation of said pulley on said shaft extending therethrough, a one-way clutch coaxial with said shaft operably connected between said pulley and said shaft for positively driving said shaft in said one rotary direction whereby said agitator is positively driven in oscillation, slip clutch means operably connected between said pulley and said shaft for driving said shaft with a predetermined maximum torque whereby said basket is driven with a limited spin-up torque, said slip clutch means including a second disc carrying a generally radial friction face parallel to said radial web, means for locking said second disc onto said shaft, and a resilient element biasing said friction face into constant engagement with said radial web with a predetermined force. 

1. In combination in a washing machine a drive pulley comprising a disc having a generally radial web extending outwardly towards a circular periphery, a belt receiving groove on said periphery, a central portion of said disc defining an axially extending hub, radial bearing means in said hub adapted to permit rotation of said pulley on a shaft extending therethrough, a second disc carrying a generally radial friction face parallel to said radial web, means for locking said second disc onto said shaft, a resilient element biasing said friction face into constant engagement with said radial web with a predetermined force, and one way clutch means for transmitting torque between said shaft and said pulley.
 2. The combination as set forth in claim 1 including a motor and a transmission for reducing the speed of said motor, said shaft being mounted on and providing a torque input to said transmission.
 3. A power drive system for a washing machine comprising a reversible rotary motor, an article receiving basket, an article agitator in the basket, a transmission including a rotatably mounted housing, an input shaft rotatably mounted in the housing, the transmission having within its housing means to reduce the speed and convert rotary motion of the motor to oscillating movement in the agitator when said input shaft is driven in one rotary direction and one-way clutch means coaxial with said input shaft to spin said housing and said basket when said input shaft is driven in the opposite direction, one-way brake means coaxial with said input shaft preventing rotation of said housing in said one direction, a drive pulley rotatably mounted on said shaft and driven by said motor through a drive belt, said drive pulley including a disc having a generally radial web extending outwardly towards a circular periphery, a belt receiving groove on said periphery, a central portion of said disc defining an axially extending hub, radial bearing means in said hub adapted to permit rotation of said pulley on said shaft extending therethrough, a one-way clutch coaxial with said shaft operably connected between said pulley and said shaft for positively driving said shaft in said one rotary direction whereby said agitator is positively driven in oscillation, slip clutch means operably connected between said pulley and said shaft for driving said shaft with a predetermined maximum torque whereby said basket is driven with a limited spin-up torque, said slip clutch means including a second disc carrying a generally radial friction face parallel to said radial web, means for locking said second disc onto said shaft, and a resilient element biasing said friction face into constant engagement with said radial web with a predetermined force. 